Taken from an Eurogamer interview with game director Lennart Sas.

Eurogamer: Many people noted the Pikmin inspiration in Overlord. Is that fair? Do you think this series effectively fills that strategic action adventure void that Nintendo has left?

Lennart Sas: We used Pikmin as inspiration, of course – but also as games such as Sacrifice; games that involved a central character who controls hordes of followers. However, I feel our core mechanics and setting are substantially different, and the games differ much more than typical shooters strategy titles. So I say anyone claiming Overlord is a Pikmin clone needs to get their head checked.

Full interview here